DiRT 2
This excellent new racer packs a nicely scriptable performance test. We tested at the game's "high" quality presets with 4X antialiasing.

The Core i5-661 takes the top spot at the lowest resolution, which counts as a victory in my book. The field groups up and becomes somewhat jumbled as the GPU bottleneck kicks in. Note, also, that the three slowest processors here all have just two cores and two hardware threads. DiRT 2 appears to benefit pretty straightforwardly from four threads.

Modern Warfare 2
With Modern Warfare 2, we used FRAPS to record frame rates over the course of a 60-second gameplay session. We conducted this gameplay session five times on each CPU and have reported the median score from each processor. We've also graphed the frame rates from a single, representative session for each. We tested this game at a relatively low 1024x768 resolution, with no AA, but otherwise using the highest in-game visual quality settings.

Lesson number one here is familiar: most games just don't need too terribly much CPU power to run well these days. Heck, our FPS minimums are in the 60s.

Relatively speaking, the i5-661 is just behind the Phenom II X4 965 and a little further behind the i5-750. One wonders what Intel was thinking when it priced the i5-661 opposite these processors. The Core i3-540, meanwhile, looks like dramatic progress from the Core 2 Duo E7600, although that Athlon II X4 630 remains formidable competition.

Source engine particle simulation
Next up is a test we picked up during a visit to Valve Software, the developers of the Half-Life games. They had been working to incorporate support for multi-core processors into their Source game engine, and they cooked up some benchmarks to demonstrate the benefits of multithreading.

This test runs a particle simulation inside of the Source engine. Most games today use particle systems to create effects like smoke, steam, and fire, but the realism and interactivity of those effects are limited by the available computing horsepower. Valve's particle system distributes the load across multiple CPU cores.

The Clarkdale processors benefit mightily here from Hyper-Threading, as does the Core i7-920.